Colo. Rev. Stat. § 32-11-528
(1) The district may issue as general obligations any of the following types of district securities, payable from taxes, or payable from taxes and additionally secured as to their payment by a pledge of net revenues or gross revenues, as the board may determine:
Source: L. 69: p. 772, § 70. C.R.S. 1963: § 89-21-70.